Transducer



United States Patent [72] Inventor Basil B. Beeken New Haven,Connecticut [21] Appl, No. 707,202 [22] Filed Feb. 21, 1968 [45]Patented Oct. 20, 1970 [73] Assignee Pitney-Bowes, Inc.

Stamford, Connecticut a corporation of Delaware [54] TRANSDUCER 5Claims, 5 Drawing Figs.

[52] US. Cl 137/81.5 [51] Int. Cl Fl5c H18, H50 3/00 [50] Field ofSearch137/8 1 .5

[5 6] References Cited UNITED STATES PATENTS 1,628,723 5/1927 Hall 137/81 .5 3,122,039 2/1964 Sowers 137/81.5X 3,144,037 8/1964 Cargilletal.137/315 I Primary Examiner-Samuel Scott Att0rneysWilliam D. Soltow, Jr., Albert W. Scribner, Martin D. Wittstein and Donald F. DaleyABSTRACT: An improved electrical to fluidic transducer including anelectrical circuit for driving a piezoelectric crystal that generatesultrasonic sound waves that are adapted to control the operation of atwo stage fluid amplifier circuit. The electrical circuit includes avoltage divider and a multivibrator for adjustably controlling theexcitation frequency of said crystal, while the fluid amplifier circuitincludes two turbulence type fluid amplifiers. A convergent passage isprovided for conducting the sound waves from said crystal to a pointadjacent the downstream end of the emitter of one of said turbulencetype amplifiers.

i ll: 48 d I MHZ, -1 l \JE3JB Hill F I :1 5/ i5 'ml is in ll" PatentedOct. 20, 1970 3,534,754

Sheet 1 of 2 Fly, i 02 4 ml 27 4 f/ .4 Ml r o lnllh H I" will I.\'\'ENTOR.

Eds/ll B. Beaker;

ATTORNEY TRANSDUCER This invention relates to an improved transducer forconverting electrical signals to corresponding fluid pressure signals.More particularly, this invention relates to a novel arrangement foroperatively coupling electrical and fluidic circuits.

There are many instances in the practical application of fiuidics wherea fluidic circuit must be controlled by the output of an electricaldevice. This situation gives rise to the need for transducing means inorder that the fluidic and electrical circuits may be properly coupled.Several arrangements have been previously proposed for such transducingfunctions however these arrangements have not always proved to beentirely satisfactory.

(Zine object of the instant invention is to provide a more efficient andreliable electric to fluid pressure transducer.

Another object of the invention is to provide a novel arrangement forelectromechanically controlling a turbulence type amplifier.

Other objects of the invention will become apparent as the disclosureprogresses.

In the drawings:

FIG. 1 is a plan view in partial section and shows the variouscomponents of the instant apparatus as mounted in a box-like housing.

FlG. 2 is a partial sectional view taken along section line 2-2 of FIG.1.

FIG. 3 is a plan view of a fluidic element circuit board which isincorporated in the instant apparatus.

FIG. 4 is a partial sectional view taken along a section linecorresponding to line tl of FIG. 3 and illustrates the fluidic elementcircuit board and associated cover plate assembly.

FIG. 5 is a circuit diagram illustrating an electrical control for theinstant transducer.

A general description of the instant apparatus will be made first inconnection with FIGS. 1 and 2. A box-like housing is provided whichcomprises a base H. with integral ends 12 and i3 and sides 14 and 15,and a cover 16 that is removably secured to said sides l4, l5 by anysuitable means such as screws 17, FIG. I. Mounted in substantiallyparallel-spaced relation in the housing 10 is a fluidic assembly I8 andan electrical control board 19. The fluidic assembly 18 is held in placeby a ridge formed on the upper surface of base it as is best seen inFIG. 2, while the circuit board 19 is slidably inserted into andretained by the slots formed by the opposed projections 20a on the innersurface of the said housing ends 12 and 13 as is best seen in FIG. 1.

The structural and functional characteristics of the fluidic assembly 18will now be considered in detail with particular reference to FIGS. 3and 4. The assembly 18 essentially comprises a two-stage fluidic circuitthat includes two fluid amplifiers 22 and 23. These two fluid amplifiersare formed by the appropriate grooving of the upper surface 24 of a mainfluidic element circuit board 25, this grooved surface then beingcovered and sealed by a suitable cover plate 26, FIG. 4, as is wellunderstood in the art. The specific fluidic circuit defined by saidgrooved surface is illustrated in FIG. 3 and comprises a fluid supplyinlet groove 30 that is formed in the board 25; said inlet groovecommunicating through a suitable groove 31 with the emitter groove orchannel 33 of said fluid amplifier 22, and also communicating directlywith the emitter groove or channel 34 of amplifier 23. Amplifier 22includes a slightly diverging (as viewed in FIG. 3) groove 35 thatdefines an interaction chamber the upstream end of which communicateswith said emitter channel 33 while the downstream end thereofcommunicates with an angularly extending venting channel 36 thatultimately extends longitudinally out through the end 37 of said circuitboard 25. The downstream end of the interaction chamber alsocommunicates with a collector groove or channel 40 that is coaxiallyaligned with said emitter groove 33. The amplifier 23 includes a widenedgroove 42 that defines an interaction chamber, the upstream end of whichcommunicates with the emitter groove 34 while the downstream end thereofcommunicates with venting channels 43 and 44), the latter extending outthrough the said end 37 of the circuit board 25.'The downstream end ofthis interaction chamber also communicates with a collector groove orchannel 4'75 that is coaxially aligned with said emitter groove 34. Acontrol groove or channel 16 communicates at one end thereof with oneside of the upstream end of said interaction chamber groove 42 while theother end thereof communicates with said collector groove 4-0 through asuitable groove or channel &7.

As is illustrated in FIGS. 3 and 4 the depth FIG. 4. of the groove 3i,said venting groove 36 and the interaction chamber groove 35 ofamplifier 22 is considerably greater than that for the emitter groove 33and collector groove 4t associated with this amplifier. In similarfashion the corresponding depth of groove 3'0, the interaction chambergroove 42 and venting channels 43, 44 of amplifier 23 is considerablygreater than that for the emitter groove 34, control groove 46 andcollector groove 45 associated with said amplifier 23. The groove andchannel configuration illustrated in FIG. 3 is approximately to scale,the typical lengths for the interaction chamber grooves 35 and d2 eachbeing in the order of five-sixteenths of an inch. One circuit boardmodel has been con structed wherein the cross-sectional size of theemitter groove 33 was made approximately .007 inches wide and .007inches deep while the cross-sectional size of the emitter groove 34- wasmade approximately .015 inches wide and .015 inches deep. Thecross-sectional sizes of collector grooves 4! and 45 were madesubstantially the same as those for said emitter grooves 33 and 34respectively. The above-noted dimensions represent only exemplary valuesand are not to be construed as being limiting values. When the coverplate as is sealingly secured to the circuit board 25, as by rivets 4band gasket 45 or by other suitable means well-l nown in the art, thevarious above-described grooves and channels will have substantiallyrectangular cross-sectional profiles.

Amplifier 22 is provided with a bell-shaped control passage 50 which isformed through the circuit board 25 and which terminates at a port Slldisposed along one side of the upstream end of said interaction chambergroove 35. The side walls 52 defining the control passage Stl arcuatelydiverge so as to form an externally facing exponentially contoured (asseen in FIG. 4) horn or sound wave receiving opening.

The side M of the box-like housing lift is formed with two appropriateapertures 60, fill, FIG. 1, through which extend flexible input andoutput fluid conduit lines s2 and 63 which are coupled respectively tofittings 65 and 66 that are integrally formed on the outer side of saidcover plate 26. These fittings are provided with passages 67 and 68which communicate with said supply groove Sid and said collector groove45 respectively; the passage 6'7 communicating with the supply grooveEltl as is diagrammatically illustrated by the phantom line 7% of FIG.3, which the passage 68 communicates with said groove 45 through arecess 71 formed in said upper surface 34 of circuit board 25.

Each of the amplifiers 22 and 23 is monostable in operation. The normalmode of operation of each amplifier is such that a laminar jet of fluidflows from the emitter and into the collector thereof whereby thepressure in said collector will be relatively high. When a suitablesignal is applied to the amplifier the fluid flow in said laminar jetwill become turbulent and this turbulent flow will interact with theside walls of the associated interaction chamber and will, for the mostpart, exhaust through the associated amplifier vent grooves leaving thepressure in the collector relatively low. This turbulent mode ofoperation will continue until the said signal is removed whereupon theamplifier will immediately resume operating in its said normal laminarmode.

Operatively mounted in a cylindrical recess 74, FIG. 4, formed in theboard 25 and substantially coaxially disposed with respect to saidpassage 5d is a piezoelectric crystal 75, said crystal being secured insaid recess by any suitable means such as the flanged button 76 that iscemented to the lower surface (as seen in FIG. 4) of board 25. A disclike pad 77 of sponge rubber or similar resilient material is mountedbetween the upper surface 760 of button 76 and the crystal 75 so as toassure proper seating, in the recess 74. of said crystal but withoutmechanically loading the latter. Two diametrically opposed slots 79 and78 are formed in the board 25 so as to allow the electric leads 80. 81access for connection with opposite sides of the mounted crystal, theseleads also being respectively connected to the adjacent terminal posts82 and 83 that are fixed to the said board 25. As will be apparent whenthe crystal 75 is electrically excited or energized at the properfrequencies the sound waves generated will pass through the exponentialhorn or passage 50 and into the interaction chamber of the amplifier 22so as to effect the fluid flow therein as will be described more fullybelow.

The means for applying electrical signals to the crystal 75 will now begenerally described in connection with FIGS. 1. 2 and 5. The saidcircuit board 19, which includes the various electrical components andinterconnections as are indicated in the circuit diagram of FIG. 5, iselectrically coupled to said terminal posts 82 and 83 by means of leads84 and 85. In FIG. 5 the circuit input terminals 100 101, are connectedacross a stepped voltage source as might be afforded by the output of anexternal electrical control system. The terminals 100 and 101 arecoupled to a conventional type adjustable voltage divider I05 the outputof which controls the transistorized multivibrator 106 in a well-knownmanner. The multivibrator 106 is coupled to a driver stage 107 in aconventional manner, and the output of this driver stage is connected tosaid crystal leads 84, 85. As will be apparent when a stepped controlvoltage is applied to terminals 100, 101, the predetermined voltageapplied by the set voltage divider 105 to the multivibrator 106 willcause the latter. through driver stage 107. to energize or excite thecrystal 75 at a desired frequency. The said units 106 and 107 arecommercially available and may each for example. be a Model #RTUL99I4integrated circuit as presently marketed by the Fairchild Company ofMountain View. California. in the instant arrangement the voltagedivider 105 is set so as to apply to the crystal 75 an ultrasonic signalfrequency in the order of 50.000 c.p.s.

I The operation of the above described transducer will now be described.Assuming the fluid supply line 62, FIG. 1. is operatively coupled to asuitable pressure source, fluid (such as air) flows through both emitterchannels 33 and 34 so that the downstream end of each of said emittersthereby issues a laminar jet of fluid that is normally directed into theassociated collector groove 40 or 45. The resultant higher fluidpressure in the collector groove 40 of amplifier 22 however, produces acontrol signal or fluid flow which passes through the control groove 46of amplifier 23 to thereby cause the latter to assume a turbulent modeof operation. With no excitation of the crystal 75 the normal state ofoperation of the instant fluidic circuit is such that amplifier 22remains in its laminar mode while amplifier 23 remains in its turbulentmode operation. Under these normal conditions the fluid pressure in thecollector 45 of amplifier 23 will be relatively low and, with thecollector 45 operatively connected through passages 70 and 68 said lowpressure condition will also exist in said output line 63. When thecrystal 75 is energized by the application of the stepped controlvoltage to the terminals 100, FIGS. 1 and 5, an effective portion of theresultant sound waves generated by the vibrating crystal 75 will passthrough the exponential horn 50 and impinge on said laminar jet issuingfrom emitter groove 33 so that the small amplifier 22 is therebyswitched from its laminar mode to its turbulent mode wherein the flow insaid laminar jet becomes turbulent and exhausts through said ventingchannel 36. The resulting pressure drop in collector 40 and the controlgroove 46 will cause amplifier 23 to switch to its laminar mode wherebythe pressure in collector 45 and said output line 63 will becomerelatively high. An interruption of said control voltage will terminatethe excitation of crystal so that the amplifiers 22 and 23 willimmediately revert to their previously described normal laminar andturbulent modes respectively whereb the fluid ressure in output line 63will again be relatively ow. As W1 be apparent then any stepped voltagecontrol signals applied to the terminals 100, 101 (which terminals asshown in FIG. I may effectively comprise a two-pronged plug 108). willbe functionally converted to corresponding pneumatic signals asrepresented by the above-described fluid pressure differentials in theoutput line 63 of the instant transducer.

The instant compact unit has been found to perform reliably andefficiently during extended periods of use.

Since many changes could be made in the embodiment of the invention asparticularly described and shown herein without departing from the scopeof the invention, it is intended that this embodiment be considered asexemplary and that the invention not be limited except as warranted bythe following claims.

l claim:

1. An electric to pneumatic signal converter comprising:

a two-staged fluidic circuit including two turbulence-type fluidamplifiers. the output of a first one of said amplifiers being connectedso as to control the operation of the second one of said amplifiers,said first one of said amplifiers including an emitter adapted to issuea laminar jet of fluid and a collector that is adapted to receive atleast a portion of the fluid issuing from said emitter;

a piezoelectric crystal mounted so as to control the operation ofsaidfirst fluid amplifier:

conduit means for conducting sound waves from said crystal to said firstfluid amplifier, said conduit means terminating at a control portlocated adjacent the downstream end of said emitter; and

electrical means for exciting said crystal.

2. Apparatus as defined by claim 1 wherein said conduit means defines apassage that converges in shape towards said control port.

3. Apparatus as defined by claim I wherein said electrical meanscomprises a voltage divider and a multivibrator.

4. A transducer comprising:

a box-like housing;

a fluidic assembly mounted in said housing;

an electrical circuit board mounted in said housing adjacent saidfluidic assembly;

said fluidic assembly including a two-stage fluidic circuit includingtwo turbulence-type amplifiers, a first one of said amplifierscomprising an emitter adapted to issue .a laminar jet of fluid;

a collector adapted to receive at least a portion of the fluid issuingfrom said emitter;

enclosure means defining an interaction chamber in the region betweensaid emitter and collector;

means defining a sound wave conducting passage, the inner end of saidpassage terminating at a small aperture disposed at the inner surface ofthe walls defining said interaction chamber and located at a pointadjacent the downstream end of said emitter;

said collector being coupled so as to control the operation of saidsecond turbulence-type amplifier;

a piezoelectric crystal adapted when excited to generate sound wave insaid passage; and

electrical means on said electrical circuit board for exciting saidcrystal which in turn will thereby generate sound waves that are adaptedto pass through said passage and small aperture so as to impinge on saidlaminar jet of fluid issuing from said emitter.

5. Apparatus as defined by claim 4 wherein said crystal is resilientlymounted at the outer end of said passage; said passage being generallybell-shaped and converging towards said aperture.

